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Well....I have a tendency to read books with lots of pages so yay for big books. The largest book I recently read would either be Henry VIII: The King and His Court or The Wars of the Roses by Alison Weir, followed by Elizabeth Gaskell's Wives and Daughters (the page numbers between these three are really close if you change the font size and the paper quality). I'm currently working through Christina Rossetti's Complete Poems, which weighs in at about 1400 pages, but that's something you just don't sit down and read cover to cover.
The single largest book I own is 30,000 Years of Art : The Story of Human Creativity Across Time and Space; it probably weighs as much as the coffee table it rests on (has awesome pictures, too).
(The "I like big books" button comes from the FB application Pieces of Flair)